A solid catalyst component that includes magnesium, titanium, an electron donor compound, and a halogen as essential components has been used for polymerizing an olefin (e.g., propylene). A number of methods have been proposed that polymerize or copolymerize an olefin in the presence of an olefin polymerization catalyst that includes the solid catalyst component, an organoaluminum compound, and an organosilicon compound.
It has been known that excellent polymerization activity and stereospecificity can be obtained using an olefin polymerization catalyst that includes a solid titanium catalyst component that supports an electron donor such as a phthalic ester, an organoaluminum compound (co-catalyst), and a silicon compound that includes at least one Si—OR linkage (wherein R is a hydrocarbon group) (see JP-A-58-83006 (Patent Document 1), JP-A-56-811 (Patent Document 2), and JP-A-63-3010 (Patent Document 3), for example). It has been widely reported that it is preferable to use a phthalic ester as the electron donor. However, di-n-butyl phthalate and benzylbutyl phthalate (i.e., phthalic esters) are designated as substances of very high concern (SVHC) specified by Registration, Evaluation, and Authorization and Restriction of Chemicals (REACH). In Europe, use of di-n-butyl phthalate and benzylbutyl phthalate will be banned from Feb. 21, 2015 in principle. Therefore, a catalyst system that does not utilize such SVHC has been desired in the industry.
A solid catalyst component that utilizes diethyl phthalate has been known as a solid catalyst component that utilizes a phthalic ester that does not fall under SVHC specified by REACH (see JP-A-10-182720 (Patent Document 4) and JP-A-57-63311 (Patent Document 5)). However, along with the banning of di-n-butyl phthalate and benzylbutyl phthalate, there has been a tendency to avoid the use of phthalic esters as an electron donor for a solid catalyst component. Therefore, a solid catalyst component for olefin polymerization and a catalyst that do not utilize a phthalic ester as an electron donor have been desired.
A solid catalyst component has been known that is prepared using a fatty acid ester (e.g., malonic ester or succinic ester) or a diether (e.g., 1,2-diether, 1,3-diether, or 1,4-diether) that does not fall under SVHC as an electron donor instead of a phthalic ester.
A solid catalyst component for olefin polymerization that utilizes a malonic ester is disclosed in JP-A-2004-91513 (Patent Document 6), JP-A-2000-516987 (Patent Document 7), JP-A-2000-516989 (Patent Document 8), and JP-A-2000-516988 (Patent Document 9), for example.
Patent Document 6 discloses a solid catalyst component that utilizes a malonic diester selected from diethyl dibutylmalonate, diethyl diisopropylmalonate, diethyl diisobutylmalonate, diethyl bis(3-chloro-n-propyl)malonate, and diethyl butylbromomalonate.
Patent Document 7 discloses a solid catalyst component that utilizes a malonic diester represented by R1R2C(COOR3)(COOR4) (wherein R1 is a hydrogen atom, R2 is a linear or branched alkyl group having 3 to 20 carbon atoms, a cycloalkyl group, or an arylalkyl group, and R3 and R4 are independently a linear or branched alkyl group having 4 to 20 carbon atoms, an alkylcycloalkyl group, a primary arylalkyl group, or a primary alkylaryl group).
Patent Document 8 discloses a solid catalyst component that utilizes a malonic diester represented by R1R2C(COOR3)(COOR4) (wherein R1 is a linear alkyl group having 1 to 20 carbon atoms, a linear alkenyl group, a cycloalkenyl group, an aryl group, an arylalkyl group, or an alkylaryl group, R1 is an alkyl group having 1 to 4 carbon atoms differing from R2, and R3 and R4 are selected from the group consisting of an alkyl group having 1 to 3 carbon atoms and a cyclopropyl group).
Patent Document 9 discloses a solid catalyst component that utilizes a malonic diester represented by R1R2C(COOR3)(COOR4) (wherein R2 is a linear or branched alkyl group having 5 to 20 carbon atoms, a cycloalkyl group, or an arylalkyl group having 7 to 20 carbon atoms, and R2 and R3 are independently an alkyl group having 1 to 3 carbon atoms or a cycloalkyl group).
JP-T-2002-542347 (Patent Document 10) discloses a solid catalyst component for olefin polymerization that includes a succinic ester represented by (R1OOC)CR2R3CR4R5(COOR6) (wherein R1 and R2 are independently a linear or branched alkyl group having 1 to 20 carbon atoms, an alkenyl group, a cycloalkyl group, an aryl group, an arylalkyl group, or an alkylaryl group that optionally includes a heteroatom, R3 to R6 are independently a hydrogen atom, a linear or branched alkyl group having 1 to 20 carbon atoms, an alkenyl group, a cycloalkyl group, an aryl group, an arylalkyl group, or an alkylaryl group that optionally includes a heteroatom, provided that R3 to R6 bonded to an identical atom optionally bond to each other to form a ring, and, when R3 to R5 are hydrogen atoms, R6 is a group selected from a primary, secondary, or tertiary alkyl group having 3 to 20 carbon atoms, a cycloalkyl group, an aryl group, an arylalkyl group, and an alkylaryl group).
A solid catalyst component for olefin polymerization that utilizes a diether is disclosed in JP-A-3-706 (Patent Document 11) and JP-A-3-62805 (Patent Document 12), for example.
Patent Document 11 discloses a solid catalyst component that utilizes a diether represented by RO—CH2CHR1R2CH2—OR (wherein R, R1, and R2 are independently a linear or branched alkyl group having 1 to 18 carbon atoms, an alicyclic group, an aryl group, an alkylaryl group, or an arylalkyl group, provided that R1 or R2 may be a hydrogen atom).
Patent Document 12 discloses a solid catalyst component that utilizes a diether represented by R1R2C(CH2OR3)(CH2OR4) (wherein R1 and R2 are an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group, or an aryl group, and R3 and R4 are an alkyl group having 1 to 4 carbon atoms).
When using a catalyst system that includes a solid catalyst component that utilizes a malonic ester or a succinic ester for polymerizing propylene, the resulting polypropylene generally has insufficient stereoregularity. Therefore, it is difficult to apply such a polypropylene to injection molding or the like for which high rigidity is required, and such a polypropylene has been mainly used as a general-purpose resin for which very high mechanical strength is not required. Moreover, since hydrogen activity is relatively high, it is difficult to apply the above catalyst system to production of a resin for which a low melt flow rate is required (e.g., sheet).
When using a catalyst system that includes a solid catalyst component that utilizes a succinic ester as internal electron donor, the resulting olefin polymer has a broad molecular weight distribution, and exhibits inferior primary properties (e.g., stereoregularity) as compared with a polymer produced using a solid catalyst that utilizes a phthalic ester as an electron donor. Therefore, it is difficult to produce resins of various grades using the above catalyst system.
When using a catalyst system that includes a solid catalyst component that utilizes a diether as an internal electron donor for polymerizing propylene, the resulting polypropylene (olefin polymer) generally has insufficient stereoregularity, and has a narrow molecular weight distribution suitable for high melt flow fibers. However, when producing a sheet, a blow molding body (e.g., bottle), a film, or a high-rigidity injection molding body, it is necessary to perform multistep polymerization while changing the amount of hydrogen, or it is necessary to use a special external donor. Therefore, the polymerization process conditions become complex, and increase in cost occurs. Moreover, since hydrogen activity is very high, it is difficult to apply the above catalyst system to production of a resin for which a low melt flow rate is required. Therefore, a further improvement has been desired.